The present invention relates to an impact beam for a door of an automotive vehicle and, more particularly, to a method and apparatus for making a heat treated side intrusion beam.
To improve safety in motor vehicles, side intrusion beams, also called side impact beams, have been designed into the passenger doors of automotive vehicles. Side intrusion beams are typically formed of steel or combinations of steel and composite materials. The side intrusion beams extend across the vehicle doors to provide occupant protection. Typically, the side intrusion beams have a beam body with a pair of brackets mounted at each end. The brackets are used to mount the beam body within the door. Commonly, side intrusion beam manufacturers provide the beam body and bracket assembly to the automotive vehicle manufacturer for installation as the doors are being assembled.
Federal motor vehicle safety standards require that side intrusion beams meet certain load or energy absorbing criteria for a specified lateral displacement of the door in response to a vehicle being subjected to a side impact. Reducing the cost of implementing the federal safety standards is an ever present goal of automotive vehicle manufacturers. Many previously known side intrusion beam assemblies require the use of relatively expensive materials and expensive material processing due to the high strength requirements.
Several examples of side intrusion beams use a beam body which is formed of heat treated steel. The beam body is subjected to heat-treating throughout the length of the beam. The beam is then welded to the end brackets that are not heat treated. Commonly, long lengths of heat treated steel material is provided to the manufacturer of the side intrusion beam. The beam body is cut to length and then welded to the end brackets. One problem with such a method for forming side intrusion beams is that purchasing already hardened steel is extremely expensive. Also, because the material is so hard, special processing techniques such as laser cutting must be implemented to properly size the beam bodies. Special processing techniques use special equipment that is relatively expensive. Another drawback to such prior beams is that because the brackets are not hardened and the entire steel bar is hardened, more stress is placed on the welds. That is, the entire beam resists bending while the brackets deform. Thus, the impact is directed to the weld area where the weld material absorbs much of the energy of impact, rather than the beam and brackets.